Not Applicable
In the past a need has existed to use waste products particularly in the thermoplastic industry for recycling into other products. These waste materials may originate from post-industrial or post-consumer sources. Recycling of thermoplastic material has been deterred due to economic considerations for processing of the waste materials into other products. Generally, waste thermoplastic materials require grinding and then extrusion into pellets for further use in an injection molding process.
In the extrusion molding process for formulation of plastic pellets, the raw material requires a sufficient resiliency to enable handling of the heated or hot materials as exiting from a die. These heated or hot raw materials may then be cooled in a water bath prior to cutting or pelletizing. The pelletized thermoplastic may then be used as starting material in an injection molding process. In an injection molding process the thermoplastic material is generally formed of polypropylene, high density polyethylene, or nylon where these materials provide a desired level of flow into a mold. The goal of the injection molding process is to form other products or component parts from the starting raw thermoplastic material. The selection of thermoplastic material in the extrusion process may have different characteristics for optimal performance as compared to an injection molding process. In the extrusion process, lubrication of the raw material for heating and feeding through the flights is of primary importance.
In the past, a need has existed for introduction of filler material to supplement raw thermoplastic waste for further processing where the filler material is used as starting material for an extrusion process to formulate thermoplastic pellets. It has not been previously known to use waste sludge from a paper mill as a source of supplementary fibers for combination with raw waste thermoplastic material for formulation of thermoplastic pellets for use in an injection molding process. A problem with the use of waste sludge from a paper mill has been the existence of an undesirable odor, excess water, and a lack of adequate lubrication.
A prerequisite to the use of waste sludge from a paper mill is to reduce the water content of the raw sludge by drying. Preferably the water content is reduced to approximately 1 percent or less. It is also desirable to use thermoplastics having relatively low melting temperatures to avoid exposure of excess heat to the sludge fibers which may result in the weakening of the strands to be used in the extrusion process.
The use of waste sludge from a paper mill in combination with waste thermoplastic material in an extrusion process yields cost effective thermoplastic pellets for further use as starting material in an injection molding process.
This invention generally relates to the formulation of thermoplastic pellets from a combination of raw sludge material from a paper mill with waste thermoplastic material from post industrial or consumer sources. Initially, waste raw sludge material is treated with a masking chemical and then transported via a conveyor to a dryer for removal of excess water. The sludge material may be additionally treated with a masking chemical at selected times throughout the formulation process. The waste thermoplastic material and the dried sludge material may then be added to a densifier where they are shredded and combined. Preferably, it is desirable to add a predetermined quantity of saw dust to the mixture of dried sludge and waste plastic. A masking chemical and lubricant may also be added to the combined waste plastic and dried sludge in the densifier. The mixture may then be transported to a grinder for grinding. The ground material may then transported to a hopper for introduction into an extruder. The ground combined material may then be subjected to an extrusion process for the formulation of thermoplastic pellets having supplemental fibers to enhance the properties for use as starting material in an injection molding process.
A principal advantage of the present invention is the provision of a formulated process for manufacture of thermoplastic pellets of relatively simple and inexpensive design, construction, and operation which is safe and which fulfills the intended purpose of providing cost-effective thermoplastic pellets for use as starting material in an injection molding process without fear of injury to individuals and/or damage to property.
Another principal advantage of the present invention is the provision of a formulation process for manufacture of thermoplastic pellets which utilizes waste raw thermoplastic material from post-industrial and/or post-consumer sources for recycling into starting material for an injection molding process.
Still another principal advantage of the present invention is the provision of a formulation process for manufacture of thermoplastic pellets which utilizes waste raw sludge material from a paper mill as a source of supplementary fibers for incorporation into thermoplastic pellets for use as starting material in an injection molding process.
Still another advantage of the present invention is the provision of a formulation process for manufacture of thermoplastic pellets which has desired fiber properties for use in an injection molding process.
Still another advantage of the principal invention is the provision of a formulation process for manufacture of thermoplastic pellets which has desired melting parameters for use in an extrusion process.
Still another advantage of the present invention is the provision of a formulation process for manufacture of thermoplastic pellets which removes any undesirable odor from the sludge material.
Still another advantage of the present invention is the provision of a formulation process for manufacture of thermoplastic pellets which has desired properties for the pellets for flow of material into a mold in an injunction molding process.
Still another advantage of the present invention is the provision of a formulation process for manufacture of thermoplastic pellets having desired lubrication properties for the material for heating and feeding through the flights of an extruder for pellet formulation.
Still another advantage of the present invention is the provision of a formulation process for the manufacture of thermoplastic pellets having a desired reduced water level for the raw sludge material for combination with recycled thermoplastic material for extrusion into thermoplastic pellets.
Another feature of the present invention is the provision of a formulation process for manufacture of thermoplastic pellets where the dried sludge and thermoplastic material are shredded and combined in a densifier with additive agents.
Another feature of the present invention is the provision of a formulation process for manufacture of thermoplastic pellets where the mixed and densified dry sludge and shredded thermoplastic material are ground into a composite material.
Still another feature of the present invention is the provision of a formulation process for manufacture of thermoplastic pellets where the ground composite material is placed into a hopper as coupled to an extruder.
Still another feature of the present invention is the provision of a formulation process for manufacture of thermoplastic pellets where the composite material is heated and compressed in an extrusion process for cooling and cutting into thermoplastic pellets for use in an injection molding process.